Particle accelerators are employed to irradiate a wide variety of materials for several purposes. One purpose is to facilitate or aid molecular crosslinking or polymerization of plastic and/or resin materials. Other uses include sterilization of foodstuffs and medical supplies and sewage, and the destruction of toxic or polluting organic materials from water, sediments and soil.
A particle beam accelerator typically includes (i) an emitter for emitting the particle beam, (ii) an accelerator for energizing and shaping the emitted particles into a beam and for directing and accelerating the energized particle beam toward a target, (iii) usually a beam scanning or deflection means, and (iv) usually a transmission window and window mounting. A generator is provided for generating the considerable voltage difference needed to power the accelerator. The generator frequently includes a power transfer apparatus, usually including a power oscillator, for supplying high voltage high frequency power to a remote load and voltage multiplication apparatus for converting the high frequency power into substantially constant high voltage DC output potential.
The emitter and the accelerator sections, which may comprise centrally arranged dynode elements or other beam shaping means, or electrostatic or electromagnetic lenses for shaping, focusing and directing the beam, are included within a high vacuum chamber so that air molecules do not interfere with the particle beam during the emitting, shaping, directing and accelerating processes.
The term "particle accelerator" includes accelerators for charged particles including, for example, electrons and heavier atomic particles, such as mesons or protons or other positive or negative ions. These particles may be charge neutralized subsequent to acceleration, usually prior to exiting the vacuum chamber.
The transmission window is provided at the target end of the vacuum chamber and enables the beam to pass therethrough to exit the vacuum chamber. The workpiece to be irradiated by the particle beam is usually positioned in the path of the particle beam, outside the accelerator vacuum chamber and adjacent the transmission window.
As used herein, the "transmission window" is a sheet of material which is substantially transparent to the particle beam. The transmission window is mounted on a window mounting comprising a support frame which includes securing and retention means which define a window envelope.
Conventionally, transmission windows are foils which have typically been installed between rectangular, generally flat flanges with filleted corners. The thin window foils are typically formed of titanium or titanium alloy sheets which typically range in thickness between about 0.0005 inches (0.013 mm) and 0.004 inches (0.104 mm). Much thicker stainless steel foils have been employed as transmission windows in irradiation apparatus for waste water/effluent processing.
Beams of this sort have many desireable uses. The efficacy of radiation-thermal cracking (RTC) and viscosity reduction of light and heavy petroleum stock, for example, has been reported in the prior art. Also, high energy particle experiments have been conducted in connection with processing of aqueous material including potable water, effluents, and waste products in order to reduce chemically or eliminate toxic organic materials, such as PCBs, dioxins, phenols, benzenes, trichloroetliylene, terrachloroethylene, aromatic compounds, etc.
Because of the known utility of particle radiation in the aforementioned processes, a need has arisen for a compact, transportable, rugged, high power, high efficiency particle accelerator apparatus. Cleland (U.S. Pat. No. 3,113,256) has suggested the use of an assembly of inductors in the shape of a toroid in an apparatus for generating high voltage high frequency (20-300 kHz) power to avoid "losses due to eddy currents", which "are prohibitively high if the usual solenoidal type inductors are used". To avoid strong radio frequency (RF) fields between opposite polarity terminals of neighboring inductors of the toroid, Cleland suggests reversing the direction of current flow and the winding sense in these adjacent inductors. Cleland points out that, in such embodiments, it is necessary to double the number of windings to obtain the same inductance that would be provided by a toroid having windings all of the same sense. Thus, reduced RT voltage stresses are obtained at the sacrifice of compactness. This particular inductor design has nevertheless been used extensively in commercial particle accelerators. The use of higher frequency RF generators would lead to a proportionate reduction in the size of their inductors and capacitors, but the limit for contemporary commercial generators used in continuous accelerators is in the range of 100-150 kHz.